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142 lines
3.1 KiB
ArmAsm
142 lines
3.1 KiB
ArmAsm
.macro ARM_DIV_BODY dividend, divisor, result, curbit
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#if __LINUX_ARM_ARCH__ >= 5
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clz \curbit, \divisor
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clz \result, \dividend
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sub \result, \curbit, \result
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mov \curbit, #1
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mov \divisor, \divisor, lsl \result
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mov \curbit, \curbit, lsl \result
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mov \result, #0
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#else
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@ Initially shift the divisor left 3 bits if possible,
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@ set curbit accordingly. This allows for curbit to be located
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@ at the left end of each 4 bit nibbles in the division loop
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@ to save one loop in most cases.
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tst \divisor, #0xe0000000
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moveq \divisor, \divisor, lsl #3
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moveq \curbit, #8
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movne \curbit, #1
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@ Unless the divisor is very big, shift it up in multiples of
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@ four bits, since this is the amount of unwinding in the main
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@ division loop. Continue shifting until the divisor is
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@ larger than the dividend.
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1: cmp \divisor, #0x10000000
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cmplo \divisor, \dividend
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movlo \divisor, \divisor, lsl #4
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movlo \curbit, \curbit, lsl #4
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blo 1b
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@ For very big divisors, we must shift it a bit at a time, or
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@ we will be in danger of overflowing.
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1: cmp \divisor, #0x80000000
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cmplo \divisor, \dividend
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movlo \divisor, \divisor, lsl #1
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movlo \curbit, \curbit, lsl #1
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blo 1b
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mov \result, #0
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#endif
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@ Division loop
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1: cmp \dividend, \divisor
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subhs \dividend, \dividend, \divisor
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orrhs \result, \result, \curbit
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cmp \dividend, \divisor, lsr #1
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subhs \dividend, \dividend, \divisor, lsr #1
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orrhs \result, \result, \curbit, lsr #1
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cmp \dividend, \divisor, lsr #2
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subhs \dividend, \dividend, \divisor, lsr #2
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orrhs \result, \result, \curbit, lsr #2
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cmp \dividend, \divisor, lsr #3
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subhs \dividend, \dividend, \divisor, lsr #3
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orrhs \result, \result, \curbit, lsr #3
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cmp \dividend, #0 @ Early termination?
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movnes \curbit, \curbit, lsr #4 @ No, any more bits to do?
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movne \divisor, \divisor, lsr #4
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bne 1b
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.endm
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.macro ARM_DIV2_ORDER divisor, order
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#if __LINUX_ARM_ARCH__ >= 5
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clz \order, \divisor
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rsb \order, \order, #31
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#else
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cmp \divisor, #(1 << 16)
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movhs \divisor, \divisor, lsr #16
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movhs \order, #16
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movlo \order, #0
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cmp \divisor, #(1 << 8)
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movhs \divisor, \divisor, lsr #8
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addhs \order, \order, #8
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cmp \divisor, #(1 << 4)
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movhs \divisor, \divisor, lsr #4
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addhs \order, \order, #4
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cmp \divisor, #(1 << 2)
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addhi \order, \order, #3
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addls \order, \order, \divisor, lsr #1
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#endif
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.endm
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.align 5
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.globl __divsi3
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.globl __aeabi_idiv
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__divsi3:
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__aeabi_idiv:
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cmp r1, #0
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eor ip, r0, r1 @ save the sign of the result.
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beq Ldiv0
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rsbmi r1, r1, #0 @ loops below use unsigned.
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subs r2, r1, #1 @ division by 1 or -1 ?
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beq 10f
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movs r3, r0
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rsbmi r3, r0, #0 @ positive dividend value
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cmp r3, r1
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bls 11f
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tst r1, r2 @ divisor is power of 2 ?
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beq 12f
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ARM_DIV_BODY r3, r1, r0, r2
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cmp ip, #0
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rsbmi r0, r0, #0
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mov pc, lr
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10: teq ip, r0 @ same sign ?
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rsbmi r0, r0, #0
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mov pc, lr
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11: movlo r0, #0
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moveq r0, ip, asr #31
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orreq r0, r0, #1
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mov pc, lr
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12: ARM_DIV2_ORDER r1, r2
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cmp ip, #0
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mov r0, r3, lsr r2
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rsbmi r0, r0, #0
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mov pc, lr
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Ldiv0:
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str lr, [sp, #-4]!
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bl __div0
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mov r0, #0 @ About as wrong as it could be.
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ldr pc, [sp], #4
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